Specific Requirements :
In the previous post we had discussed about the general requirements relating to the vendor drawing review (VDR) for the manual valves. But there are few requirements which are specific depending upon the type of the valves.
These requirements are specified below based on valve type-
Gate, Globe & Check Valves
- Check type of Wedge (solid, flexible) or disc specified (tapered plug/flat/guided plug type/needle type etc.)
- Check for stelliting / hard facing requirements as specified.
- Check for requirements of integral by-pass valves and pipe, for gate valves for larger sizes (>= 350 mm) and for high pressure valves.
- Check for back-seating requirement for gate, globe and piston valves.
- Check for physical interference for large gear operated valves. (It is possible to rearrange the orientation of gear box).
- Check for construction of Rising Hand wheel or Non rising Hand wheel requirements.
- Check if spring is provided for spring-loaded check valves.
- Check for “gas column” (extended stem or bonnet) for valves in low temperature service.
- Check for spindle support details for extended spindle valves.
- Check for retainer less design in case dual plate check valves.
- Check for disc opening not fouling with the adjacent flange ID in case of dual plate check valves.
- Check disc inclination of swing check valves; it shall be minimum 5°.
- Check for renewable seat rings wherever it is specified in the specification.
- Check for vent/drain requirements if any.
- Check for requirement of pressure seal bonnet.
- Specify marking of open/close direction on hand wheel.
- Check for stem retention design, number of packing rings for gate, globe and piston valves.
- Check for number of turns of hand wheel requirement to be specified in the drawing.
- Check for Cv value of globe valves requirement as per process if any.
- Check for pressure drop compliance and maximum flow rate as per process in case of non-slam check valves.
- Read more about – Gate valve, Globe valve , Check Valves
- Check Body construction – whether Single (Top entry) /2 or 3 piece (Side entry) / fully welded type.
- Check floating type or trunnion type as per project specification.
- For floating ball valves pressure balancing hole in ball valves should not be there unless specifically agreed during ordering.
- In case of valves with 2 or 3 piece design construction check for space availability between end flange and body flange for proper bolting of line flanges.
- Check provision of features such as seal/seat ring arrangement, soft / metal seated, primary soft and secondary metal to metal seat, and primary metal to metal and secondary soft seat design requirements as specified.
- Check provision for fire-safe design, anti-static device, blow-out proof stem, regular/reduced (reduction to one size only in general and in higher sizes can be two size also to be verified with process case by case or according to project requirements) or full bore etc.
- Check the minimum bore diameter according to design standard.
- Check for weld overlay requirements of CRA materials in seat pocket, stem seal areas/tungsten hard facing requirements / ENP coating thickness requirements.
- Check for vent /drain arrangements (flanged, threaded, etc.) and sizes as required.
- Check for Double O-ring protection requirements as specified.
- Check for emergency stem / seat sealant injection fitting arrangements as specified. (In case of PTFE+Elgiloy seat seals provided, seat sealant fittings are not recommended based on orientation of seals).
- Check if stem-extension is provided as called for to accommodate thermal insulation/ operability from further point. The extended stem shall be positively secured with main stem so that it shall not be lifted from its position.
- Check the details and suitability of seat and seal material with respect to temperature, fluid service compatibility (H2S, CO2, etc.,), and resistance to explosive de compression for gas service. VITON shall not be used for Amine service and for sour service with above 0.2% of H2S.
- HNBR seals may be used up to 5% H2S in case of sour service. (It is necessary to furnish fluid information to the manufacturer for his best recommendation of seat and seal materials).
- In case of soft seated valves welded end connections, pup piece length shall be sufficiently long so that soft material is not damaged during welding at site especially where the welds need to be PWHT at site. Check the requirement of PWHT for pup pieces.
- If the valve pressure temperature rating is different from the standard (ASME) check, whether this is acceptable or not.
- Check PT curve for offered soft seat material.
- In case of cladded valves ensure that LTCS/CS portion is not exposed to process fluid. Inconel 625/825 sleeve design shall be with TEE type arrangement.
- Space for nut installation on flange face (line bolting) shall be verified for small bore valves especially valves with 2 piece design.
- Check the liner thickness of the fully lined valves.
- Check for the provision of cavity relief hole on the upstream side of ball, if called for. Consequently valve turns out to be unidirectional; check whether flow direction is indicated for such cases.
- Read more about – Ball Valve , Ball valve design based on body contruction
- Check for body construction i.e., wafers type, lugged wafer type etc., as specified.
- Check for disc design requirements i.e., concentric, double off-set or triple offset.
- Check if wafer ends are suitable for mounting between flanges specified. (Some wafer designs have two or more bolt holes either drilled or drilled and tapped. The later may require cap screws for mounting the valve).It is preferable to include bolts in the scope of supply of valve manufacturer with required spares.
- In case of bolts included in the valve supplier’s scope, ensure that any additional bolt length requirement for mounting of insulating gaskets or spectacle blind/ spacer & blinds are taken care as per requirements of P&ID / Isometrics.
- Check for bolt threading details like standard and length of threaded portion.
- Check if manufacturer’s pressure class is equal or more than what is specified.
- Check for provision of throttling lever as specified for lever operated valves and enclosed gear operator for gear operated valves.
- Check if valve is provided with body sleeve as called for. (Some manufacturers provide body sleeves which are not replaceable. This is acceptable based on experience of such a design. For process application, check the lining and encapsulation of disc as specified).
- Check for disc coating (may be EPDM or Epoxy or Chromium plating on the disc edge), hardness of lining requirements.
- Check for disc opening not fouling with the adjacent flange ID in case of butterfly valves.
- Check whether torque calculation has been provided, if called for.
- Check for provision of integral supports, if called for.
- Check UL/FM certification requirement for fire water service.
- Read more about – Butterfly Valve
Double Block & Bleed Valves / SBB Valves
- Check for valve type based on the data sheet whether block valves are of ball type or gate type or globe type.
- Check for construction whether it is slim line mono flange, end entry either one piece or split (integral or flanged type), end connections are of flanged/threaded ends or flanged/ flanged ends.
- Check for face to face dimensions as per manufacturers standard shall be as short as possible.
- Check for minimum bore requirements for block valves as specified normally it is 10 mm for ½” NB or as indicated in the datasheet, for bleed valves which are of needle/globe type shall be 5 mm or as indicated in datasheet.
- Check for sealing arrangements in case of threaded end connections/adapters.
- Check for hand wheel/lever operatability and diameter.
- Check for fire safe design/ fire tested design in case of soft seated valves as per requirements.
- Check for full bore requirement if any.
- Check for any specific requirements on the gap between handles if oriented in the same direction.
- Read more about – Double Block & Bleed Valves / SBB Valves
- For jacketed plug valves, bolt clearance dimensions shall be verified so that line bolts can be installed.
A) Lubricated plug valves:
- Check for provision of lubricated passage to the sealing surfaces.
- Check for provision of pressurized lubricant.
- Check for provision of integral ball type check valve to prevent back flow of lubricant from the seats.
- Check for the compatibility of the lubricant with the fluid handled.
- Check if each valve of each size is to be provided with a lever or a common lever acceptable for a group of valves.
B) Sleeved plug valves:
- Check the material for the sleeve.
- In case of lined plug valves, check the material for the body lining as well as the lining for the plug. These may be different (PTFE, FEP for example) as per manufacturer’s standard.
- Check for fire-safe design, if specified.
- Check for stem extension for insulated valves, if required.
- For multi-port valves, check the arrangement of ports as per the flow requirements.
- Check for antistatic device.
- Read more about – Plug Valves
- Check body type – weir or full port. In case of valves with PTFE diaphragms, normally weir type construction is possible.
- Check the material of diaphragm, body lining (in the case of lined valves).
- Check the provision of sealed bonnet and V-notch vent plug to check the integrity of diaphragm.
- Valves shall be provided with “Travel Stop”.
- Check the type of piston – throttling or non-throttling.
- Check the materials for upper and lower sealing and their suitability for the process fluid, pressure and temperature (it is necessary to furnish fluid information to the manufacturer for his best recommendation of sealing ring materials).
- Check the valve body rating. These could be different from ASME standards by some manufacturers.
- Check the provision of back-up gland packing.
- Read more about- Piston Valve
Bellow Sealed Valves
- Check the provision of bellow and its material of construction.
- Check if back-up gland packing is provided.
- Check for bellow cycle life mentioned. This shall be a minimum of 5000, if not specified in project documents.